I'll believe it when I see it.
Unless they've changed since I could still see to play them, the typical MMORPG was nothing more than a "kill it, loot it, go buy better stuff, lather-rinse-repeat" style grind. Sure there were NPC's you could interact with to try & make it NOT so bloody & bloody minded, but the bulk of it was of the kill-it-and-sell-it variety. Of course an AI would excell at that, there's not much for it to do.
My typical D&D session was full of complex problem solving, diplomatic conflict avoidance/resolution, a giant treasure hunt, puzzle solving, poetry deciphering, "how can I steal the dragon's hoarde without getting myself eaten?" style of adventure. There was so many different probability tree branches, things going wrong that you had to crisis resolve on the fly, try to outsmart the DM so you could live to enjoy your winnings, madcap of action that I doubt any AI could ever make a decent show of itself.
I'll believe an AI can play D&D (versus a mere MMORPG) when I can watch it tackle a random module & survive the first time through. Our characters often didn't get ressurrected so why should the AI enjoy it either? "Bob the Barbarian" only got one try, after he died we had to Roll A New Character ("HA! You died! RANC! Muh Hahahahaha!") & come back as Jill the Ranger or Vicki the Viking or Sammy the Psycho Sorcerer.
Your typical MMORPG is a simple thing the AI can thrive in by simply killing everything not itself. Your typical D&D adventure would end very shortly if the AI killed off that first NPC whose job it was to tell them what their quest was in the first place. If I or my DM's were any indication then such a "kill 'em all" player tended to die thirty seconds after slaughtering the kindly old man whom wanted to hire the party to find his kidnapped daughter. See how the AI's job isn't an easy one? And *that* is why I don't believe AI's can play D&D.